1. Technical Field
The present invention relates to actuator devices for liquid ejecting heads. More specifically, the present invention relates to actuator devices which include vibrating plates and piezoelectric elements that are displaceably provided on a substrate.
2. Related Art
Typically, the piezoelectric elements used in actuator devices have a structure wherein a piezoelectric material, such as a piezoelectric layer made of a crystallized dielectric material, which functions as an electromechanical transducer is disposed between a lower and upper electrode. These actuator devices are typically called flexural-oscillation-mode actuator devices, and are often used in liquid ejecting heads, such as those used in ink jet recording heads, wherein a series of vibrating plates constituting part of pressure-generating chambers communicating with the nozzle openings of the recording head are deformed by the piezoelectric elements. By deforming the vibrating plates, the ink in the pressure-generating chambers is pressurized and ultimately ejected as ink droplets through the nozzle openings of the liquid ejecting head.
In some configurations, a separate piezoelectric element is independently formed for each pressure-generating chamber in a lithographically process wherein a piezoelectric material layer uniformly deposited over the entire surface of the vibrating plates is divided so as to correspond with each pressure-generating chamber. For example, Japanese Patent Applications JP-A-2002-314163, JP-A-2002-319714, and JP-A-2003-174211 disclose examples of independently formed piezoelectric elements which include a lower electrode disposed on a substrate, a piezoelectric layer disposed on the lower electrode, and an upper electrode disposed on the piezoelectric layer, such that one end of the lower electrode and is perpendicular to the top surface of the substrate.
One problem with these configurations, however, is that operating the piezoelectric element of the actuator result in cracks in the piezoelectric layer as the stress from the actuation causes a concentration of stress at the boundary between the upper and lower electrode comprising the active piezoelectric region and the remaining inactive portions of the piezoelectric region.